Retractable aircraft antenna with streamlined radome for scanning

ABSTRACT

A rotatable antenna selectively positionable to an operative location beneath the underside of the fuselage of an aircraft; the antenna being capable of being of a greater longitudinal length than the diameter of the aircraft fuselage, and being selectively retractable, vertically, to a stored position entirely within the aircraft fuselage.

United States Patent Rempt [451 Apr. 11, 197 2 [54] RETRACTABLE AIRCRAFT ANTENNA [56] References Cited ITH STREAMLI E g N D UNITED STATES PATENTS 2,674,420 "4/1954 Johnson ..343/872 [72] Kemp" Van Nuys Cahf- 2,702,346 2/1955 Evans et al ....343/872 [73] Assignee: Lockheed Aircraft Corporation, Burbank, 2,984,834 5/ 1961 Howard at Calif. 3,026,516 3/1962 Davis ....343/70s 3,045,236 7/1962 Colman et al ..343/705 [22] Filed: Dec. 4, 1969 Primary Examiner-Eli Lieberman [21] Appl' Attorney-George C. Sullivan and Ralph M. F lygare [52] US. Cl ..343/705, 343/725, 343/765, [57] ABSTRACT 343/872 A rotatable antenna selectivel y positionable to an operative [51] hit. Cl. ..H0lq 1/28 location beneath the underside of the fuselage of an aircraft; [58] held M Search "343/705, 3 2577 6 5 the antenna being capable of being of a greater longitudinal length than the diameter of the aircraft fuselage, and being selectively retractable, vertically, to a stored position entirely within the aircraft fuselage.

7 Claims, 6 Drawing Figures PATENTEDAPR 1 1 I972 SHEET 2 [1F 2 FIG. 5

INVENTUR. HENRY F REMPT RETRACTABLE AIRCRAFT ANTENNA WITH STREAMLINED RADOME FOR SCANNING BACKGROUND OF THE INVENTION It is relatively common for military airplanes which engage upon search and detection missions to employ the use of a radar antenna. Such antennas are usually carried within an aerodynamic body commonly referred to as a radome. The radome must be exposed externally of the airframe to operate effectively and as such radomes are of considerable bulk, a serious problem results from the standpoint of placement as well as that of aerodynamic drag. To permit a scanning movement of the antenna, either the radome must be of such proportions as to permit movement (e.g. rotation) of the antenna within the fixed radome or, the radome and the antenna are moved together as an integral unit. In either case, such radomes preferably have their greatest overall dimension greater than the width of the aircrafts fuselage. While it is common to tolerate these problems through the use of a fixedly positioned radome located on the underside of the aircraft fuselage, it is highly desirable to eliminate the above noted difficulties. The increased aerodynamic drag caused by a fixed radome likewise increases fuel consumption and lowers the maximum speed of the aircraft. When the airplane is enroute from its ground base to its patrol station it would be of greater efficiency to eliminate the drag imposed by a fixed radome. It would be desirable to overcome the above difficulties as by stowing the radome within the interior of the fuselage of the airplane.

Heretofore, there have been attempts at designing radomes of the type to enclose either fixed or rotating antennas to overcome the above noted difficulties. One such mounting of a radome provides for displacement of the radome from an operating position at the underside of the aircraft to a stowed position at an exterior location on the side of the fuselage, thereby avoiding interference with landing operations. However, undesirable drag is present with such repositioning radome systems as well as the undesirable complexity required for the mechanical structure to effect such repositioning.

A technique used to lower aerodynamic drag is to actually retract the radome within the fuselage of the aircraft except while in active use. Heretofore, such radomes have been retracted by means of rather complex mechanical structure which increases the chance of mechanical failure as well as the increase in weight. Also, all known previous retractable radomes are fixed in position during active use and are not rotatable. Thus, the radome must be of such dimension as to permit scanning of the antenna within the fixed radome.

SUMMARY OF THE INVENTION The mounting of a radar antenna structure in conjunction with the fuselage of an aircraft wherein: The radar antenna structure is supported within an aerodynamic body referred to as a radome, the radome being selectively positionable exterior of and adjacent the underside of the aircraft fuselage, the radome being rotatable when in the exterior position, the radome being movable vertically to be entirely retractable within the aircraft fuselage, the retracting and rotating mechanisms being non-complex in design. Retraction of the radome while enroute to the patrol station provides effective concealment of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of the apparatus of this invention showing its operative position in relation to an aircraft.

FIG. 2 is an enlarged cross-sectional view of the apparatus of this invention taken along line 22 of FIG. 1.

FIG. 3 is a cross-sectional view taken along line 33 of FIG. 2.

FIG. 4 is a partly in cross-sectional view taken along line 4 4 of FIG. 2.

FIG. 5 is a view similar to FIG. 2 but showing the apparatus of the invention in the retracted position.

FIG. 6 is a cut-away partly-in-section view taken along line 6--6 of FIG. 5 showing the rotating radome mechanism employed in this invention.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENT Referring particularly to the drawings, in FIG. 1 there is shown an aircraft 10 having a fuselage 12 and wings 14. The radome mechanism 16 of this invention is shown located on the underside of the fuselage 12 in the operative position. Radome I6 is to include any conventional type of radar apparatus, it having been found to be satisfactory to include a forward-looking radar antenna 18 in the nose portion of the radome l6 and a reflector and/or a flat type antenna in the central and aft portion of the radome 16. An internally mounted reflector having a width substantially as great as the length of the major axis of the radome 16, is indicated at 20. The forward-looking antenna 18 is used for enroute surveillance, with the radome 16 having its major axis maintained in stationary alignment with the longitudinal axis of fuselage 12. It is to be observed from the drawings that the radome I6 is constructed to have a streamline shape to lessen aerodynamic drag with the nose portion being substantially identical in shape to the aft portion. The radome 16 is constructed principally of a dielectric material substantially transparent to radar signals, and internal supporting structure.

There is shown in FIG. 3 the manner in which the antennas for use on station may be mounted within radome 16. First, it should be understood that the radome itself (16) is designed for the particular frequency range of interest, as will be apparent to those versed in the art. Also, a number of large aperture antennas may be mounted within the single radome 16. By way of example, search antennas 19, 21, and 23each designed for a different operating frequency-may be mounted adjacent multiple antennas 25. These antennas (I9, 21, 23 and 25) may be either flat or reflector type search antennas for use on station, and in the case of reflector-type antennas they may be adapted to cooperate with reflector 20. One or more antennas may be used to perform a search function while others perform an electronic countermeasure (ECM) function. Other variations will be readily apparent to those versed in the art.

Although not shown in the drawing, it will be understood by those skilled in the art, that any suitable waveguide plumbing or the like may be used to couple antennas 19, 21, 23 and 25 to ancillary radar or ECM apparatus within fuselage 12. Also, power means may be employed within radome 16 to nutate or otherwise scan the antennas about a minor or elevation axis, in a manner which will be readily comprehended by those versed in the art.

Connected to radome 16 is a rotating motor housing 22 within which is mounted shaft 24. Preferably housing 22 is fared so as to be streamlined and thereby reduce aerodynamic drag. Radome 16 is angularly movable with respect to housing 22. Shaft 24 is permanently affixed to the radome 16 by means of disc 26 connected to radome plate 28. Permanently affixed to shaft 24 is a gear 30 which is capable of being rotated by means of worm gear 32 through motor 34. Motor 34 is permanently affixed to the bracing plate 36 of the motor housing 22. Upon arriving at its patrol station, the aircrafts (10) radome 16 is rotated in azimuth and the flat or reflector antenna 20 is placed into operation. Antennas 19, 21, 23 and 25 may be of large aperture as compared with the forward-looking antenna 18.

A beam 38 is permanently affixed to an upper plate 40 of the housing 22. Pivotally attached to each end of beam 38 is a fore linkage arm 42 and an aft linkage arm 44. Pivotally attached on each side of arm 42 are braces 46 and 48 which are pivotally attached to trunnions 50 and 52, respectively. In a like manner pivotally attached to each side of arm 44 are braces 54 and 56 (not shown) which are pivotally attached to 3.

trunnions 58 and 60 (not shown), respectively. Each of the trunnions 50, 52, 58 and 60 are permanently attached to a portion of the fuselage 12. Fore linkage arm 42 terminates in a roller 64 which cooperates with a roller guide 62. Guide 62 is permanently affixed to fuselage l2. Aft linkage arm 44 likewise terminates in a roller 66 which cooperates with roller guide 68. Guide 68 is also permanently affixed to fuselage 12.

Approximately centrally attached to beam 38 in a freely rotating manner is jack screw 70 which is threadingly connected within screw housing 72. A motor assembly 74 operates upon jack screw 70 and causes jack screw 70 to longitudinally move relative to housing 72.

The above-described structure minimizes the non-uniform drag effects of the radome and also avoids adverse bending moments.

The operation of the apparatus of the invention is as follows: With the radome 16 in the non-operative stored position within the fuselage 12 as shown in FIG. 5, there is no aerodynamic drag caused by the radome apparatus. To deploy the radome 16, the aircraft pilot causes the opening of doors 73 located in the fuselage skin (similar to aircraft bomb-bay doors) which will permit exit of the radome 16. Motor 74 is then activated causing extension of screw 70 and outward movement of radome 16. The rollers 64 and 66 of the arms 42 and 44, respectively, move within their respective guides 62 and 68 toward each other. Braces 46, 48, 54 and 56 pivot about their respective trunnions through a total angular movement of approximately 15 with braces 46 and 48 pivoting counterclockwise and braces 54 and 56 pivoting clockwise. The function of braces 46, 48, 54 and 56 is to provide lateral support for the radome 16 when fully extended. With the radome 16 fully extended, as shown in FIG. 2 of the drawings, motor 34 can be activated causing angular rotation of the radome 16. Such rotation provides the desired. scanning in azimuth of the radar antennas 19, 21, 23 and 25. Motor 34 can be a reversible motor, thereby permitting rotation of the radome 16 in either direction. In a typical construction, motor 34 may cause radome 16 to rotate at a rate of RPM. Peak horsepower requirements in a typical construction are approximately 61 HP at an azimuth angle of 130 and an aircraft speed of 206 miles per hour, and an altitude of 10,000 feet. It should be understood that the speed of the aircraft while on station is substantially reduced, as compared with the enroute speed. As a consequence, the imposed drag penalty when the radome is deployed into the airstream, is acceptably low.

To again retract and store the radome 16, it is only necessary to rotate radome 16 to align its major axis longitudinally with respect to the fuselage 12 and thereby permit entry, through the doors 73, within the fuselage. Thereupon the reverse of the foregoing procedure is instituted until complete retraction and storing of the radome 16 is achieved.

In a typical construction, radome 16 may have overall dimensions of 30 feet long by 6 feet wide by 3 feet high, and be streamlined or lentil shaped to result in minimal parasitic drag. If desired, however, it may be further shaped to employ aerodynamic effects which will aid in its rotation while on station, by means of a windmilling effect, thereby reducing the size of motor required for rotation of the radome. The pylon or housing 22, and shaft 24 may be canted downwardly at an angle of approximately 6 from the fuselage reference line, as this is the angle which will permit the axis of antennas l8 and 20 to remain most nearly horizontal at the normal operating attitude of the aircraft 10. In addition to the previously mentioned advantages of the present invention, the extension of the radome 16 from the fuselage 12 will materially reduce spurious reflection of radar signals from aircraft 10. When in the stowed or retracted position, radome 16 will avoid ground clearance problems during takeoff and landing.

While on station, the rotating search antenna has very little effect on either the longitudinal static stability or the trim of the aircraft 10. However, there results a cyclically changing drag increment. A compensating feature of the present invention, as compared with conventional fixed external large-aperture antenna radomes, is that the drag is low when it is not operating. The range and endurance of the aircraft are not adversely effected by the high average drag when operating, due to the lower drag enroute. That is, a favorable tradeofi results in the usual case since the drag is low while the aircraft is flying at high speed to the search and surveillance area, and the aircraft flys slow on station while the radome is deployed.

If desired, automatic throttle control means or the like may be employed to synchronously adjust the instantaneous speed of the aircraft with the rotation of the radome in order to maintain a constant forward speed of the aircraft.

While the preferred embodiment of the invention provides for retraction of the radome into the fuselage while the aircraft is landing or enroute, it should be understood that the invention as herein contemplated need not include this retraction feature. That is, the essential feature of the invention is the centrally supported, elongate, radome which may be rotated while the aircraft flys at low speed on station and which may be fixed in a minimum drag configuration while the aircraft flys at high speed enroute. In those instances where the aircraft has adequate ground clearance during landing for a downwardly depending radome structure, the retraction feature may be omitted. In such a case, the benefit of the invention derives from the fact that the rotordome may be lined up with the major axis of the fuselage for low drag, yet have aperture dimensions greater than the width of the fuselage while in the rotating mode.

Other modifications of the invention will be apparent to those versed in the art.

What is claimed is:

1. In an aircraft having an elongate fuselage, airborne antenna apparatus comprising:

an elongate radome having a generally lentil-shaped cross section and having first and second streamlined ends, the longitudinal dimension of said radome being greater than the width of said fuselage and the transverse dimension of said radome being smaller than the width of said fuselage;

a moving means for effecting displacement of said radome from a stowage position within said fuselage to an operating position exteriorly of said fuselage, said moving means effecting motion of the radome along a generally straight vertical line;

means secured to said moving means rotatably mounting said radome to permit azimuth rotation of said radome when extended exteriorly of said fuselage;

selectively operable means for fixedly locking said radome exteriorly of said fuselage during high-speed flight of said aircraft to an aligned position wherein the major axes of said fuselage and said radome are substantially parallel, thereby minimizing parasitic drag; and

selectively operable means for continuously rotating said radome exteriorly of said fuselage during low-speed flight in a plane of rotation which is substantially coplanar with the flight path of said aircraft.

2. Airborne antenna apparatus as defined in claim 1 including:

a first forward-looking antenna, the maximum dimension of which is less than said transverse dimension, housed within said first end of said radome and having a beamed radiation pattern directed generally outward therefrom in substantially coaxial alignment with the longitudinal axis of said radome; and, v

a second large-aperture scanning antenna, the maximum dimension of which is greater than said transverse dimension and less than said longitudinal dimension, housed within said radome and disposed along the major axis thereof and having its radiation pattern directed generally perpendicular to the beam axis of said first antenna.

3. Airborne antenna apparatus as defined in claim 2 includmeans for selectively operating said forward-looking antenna when said radome is fixedly locked and for selectively operating said scanning antenna when said continuously rotating means is in operation.

4. Airborne antenna apparatus as defined in claim 1 angle is approximately 6. wherein said continuously rotating means comprises 7. An apparatus asdefined in claim 1 wherein: aerodynamic surfaces disposed on the ends of said radome, id moving means comprises a pair of pivotal arms, one and responsive to the forward motion of said aircraft, to imend of each f Said arms being low f i ti ll movable g rotatiotn thereto t d f d 1 1 within a guide, each of said arms having a pair of braces 1r orne an enna appara us as e me m c a1m pivotally attached thereto; and

wherein Said mounting means and said rotating means amotor driven 'ack screwo erabl connected to the other cooperate to cause said plane of rotation to be canted J p y downwardly, in the direction of said flight path, with respect ends of i arms for eXtendiPg retrafiting Said rotatato the fuselage reference line of said aircraft. 1() ble moummg means along Sald smgle Stralght 6. An apparatus as defined in claim 5 wherein: said cant 

1. In an aircraft having an elongate fuselage, airborne antenna apparatus comprising: an elongate radome having a generally lentil-shaped cross section and having first and second streamlined ends, the longitudinal dimension of said radome being greater than the width of said fuselage and the transverse dimension of said radome being smaller than the width of said fuselage; a moving means for effecting displacement of said radome from a stowage position within said fuselage to an operating position exteriorly of said fuselage, said moving means effecting motion of the radome along a generally straight vertical line; means secured to said moving means rotatably mounting said radome to permit azimuth rotation of said radome when extended exteriorly of said fuselage; selectively operable means for fixedly locking said radome exteriorly of said fuselage during high-speed flight of said aircraft to an aligned position wherein the major axes of said fuselage and said radome are substantially parallel, thereby minimizing parasitic drag; and selectively operable means for continuously rotating said radome exteriorly of said fuselage during low-speed flight in a plane of rotation which is substantially coplanar with the flight path of said aircraft.
 2. Airborne antenna apparatus as defined in claim 1 including: a first forward-looking antenna, the maximum dimension of which is less than said transverse dimension, housed within said first end of said radome and having a beamed radiation pattern directed generally outward therefrom in substantially coaxial alignment with the longitudinal axis of said radome; and, a second large-aperture scanning antenna, the maximum dimension of which is greater than said transverse dimension and less than said longitudinal dimension, housed within said radome and disposed along the major axis thereof and having its radiation pattern directed generally perpendicular to the beam axis of said first antenna.
 3. Airborne antenna apparatus as defined in claim 2 including: means for selectively operating said forward-looking antenna when said radome is fixedly locked and for selectively operating said scanning antenna when said continuously rotating means is in operation.
 4. Airborne antenna apparatus as defined in claim 1 wherein said continuously rotating means comprises aerodynamic surfaces disposed on the ends of said radome, and responsive to the forward motion of said aircraft, to impart angular rotation thereto.
 5. Airborne antenna apparatus as defined in claim 1 wherein said mounting means and said rotating means cooperate to cause said plane of rotation to be canted downwardly, in the direction of said flight path, with respect to the fuselage reference line of said aircraft.
 6. An apparatus as defined in claim 5 wherein: said cant angle is approximately 6*.
 7. An apparatus as defined in claim 1 wherein: said moving means comprises a pair of pivotal arms, one end of each of said arms being low frictionally movable within a guide, each of said arms having a pair of braces pivotally attached thereto; and a motor-driven jack screw operably connected to the other ends of said arms for extending and retracting said rotatable mounting means along said single straight line. 